Patent GB-754334-A (GB)
Title: Improvements in or relating to flight simulating means with stabilizing control
IPC: G09B9/20
Filed: 1953-10-26
Abstract: 754,334. Flight training apparatus. DEHMEL, R. C. Oct. 26, 1953, No. 29523/53. Class 4. [Also in Group XXXVI] An aircraft flight simulating apparatus comprises multiple interacting and interconnected flight computing servo-systems, each representing an altitude or translation condition of an aircraft in flight, comprising an airspeed servo-system responsive to simulatedattitude and velocity controls, a rate of pitch servosystem responsive to a simulated elevator control, a pitch angle servo-system responsive to the computed rate of pitch angle, and a rate of climb servo-system responsive to the computed simulated airspeed and pitch angle; there being provided indicators of the simulated flight conditions responsive to the respective servo-systems and stabilizing means for applying a signal representing the second time derivative of simulated altitude to -the rate of pitch computing servo-system to simulate the damped oscillations of an aircraft in flight about its equilibrium pitch altitude. Airspeed simulation.-A servo-system for computing simulated air speed comprises a summation amplifier 100 energizing the control coil of a bi-phase motor 101 whose remaining coil is energized by a reference voltage e1 which drives a bi-phase generator 101a excited by a reference voltage e2, linear potentiometers 103, 108 and square law potentiometer 104. The input of the amplifier comprises a degenerative rate signal Efb from the generator and a voltage T simulating engine thrust derived from potentiometer 109 whose slider is adjusted by the simulated throttle control to represent engine horsepower and energized from potentiometer 105 by a voltage proportional to the reciprocal of the air speed V represented by the servo- HP system rotation, since T = --. Amplifier V 100 also receives input voltages CD (representing drag as a function of the angle of attack α) derived from the subsequent angle of attack servo-system, a degenerative voltage proportional to (- V<SP>2</SP>) from potentiometer 104 (representing drag coefficient as a constant function of airspeed) and a voltage Gv representing the airspeed component of gravity along the flight path from the pitch angle (#) servosystem. The airspeed computing servo-system therefore assumes a position at which the algebraic sum of the inputs is zero, and the displacement representing V deflects a simulated airspeed indicator 24. Angle of attack simuLation.-A similar servosystem computing angle of attack α comprises an amplifier 112 energizing a bi-phase motor 111 and generator 111a as before to drive potentiometers 116, 117, 118, and 140. Potentiometer 116 is centre-tapped to earth, energized by a (V<SP>2</SP>) voltage at its opposite ends from the slider of potentiometer 104, and contoured to represent the coefficient of V<SP>2</SP> in the formula where CD (a) is the simulated drag coefficient; p is the simulated density of air; D is the simulated drag in lb. ; S is the simulated projected wing area; and the slider voltage CD representing drag is fed to the input of amplifier 100. Potentiometer 117 is centre-tapped to earth and fed at its opposite ends by antiphased V<SP>2</SP> voltages from the slider of potentiometer 104 and contoured to represent the coefficient CL (a) of V2 in the formula where CL (α) is the simulated lift coefficient; L is the simulated lift in lb.; and the slider voltage CL representing lift is fed to the input of amplifier 112 with voltages Gα and FC representing respectively the gravity component perpendicular to the flight path and centrifugal force (FC=V#y) from potentiometers 119 and 129 of subsequent pitch (#) and rate of pitch (#y) servo-systems. The servosystem therefore assumes a position at which the algebraic sum of the inputs is zero and the displacement is proportionate to the angle of attack α. Pitch angle simulation.-A similar servosystem computing pitch angle # comprises an amplifier 120 energizing a bi-phase motor 121 and generator 121a as before to drive potentiometers 119 and 142 in response to a degenerative rate input signal Efb and a signal representing rate of pitch wy from potentiometer 130 of the subsequent wy servo-system. The pitch angle servosystem runs to zeroize its total input at a displacement representing ##y=#, and is geared to operate the sliders of potentiometers 119 and 142 together with the pitch element of a simulated attitude gyro. Potentiometer 119 is cosinusoidally contoured and earthed at points 180 degrees apart while being energized intermediately of the grounded points with constant antiphased voltages E representing climb and dive gravity values respectively. 90 degree spaced slider contacts 122, 123 derive voltages Gv= - W sin # and Gα=W cos #, where W is the simulated aircraft weight, representing the gravity components along and perpendicular to the flight paths to energize the inputs of the airspeed (V) and angle of attack (α) servosystems. Potentiometer 142 is co-sinusoidally contoured, earthed at 180 degrees spaced points intermediate of its ends, energized with simulated airspeed signals V in antiphase between its ends and its centre-point, derived from potentiometer 103, and is provided with 180 degrees spaced sliders 142<SP>1</SP>, 144 driven by the pitch angle (#) servo-system to derive antiphased V cos # signals, and an intermediate similarlydriven slider contact 143 deriving signals representing V sin #. Rate of pitch simulation.-A similar servosystem computing rate of pitch (#y) comprises an amplifier 125, energizing a bi-phase motor 126 and generator 126a to drive linear potentiometers 129, 130 in response to a rate feed-back input signal Efb from the generator 121a, a signal representing the pitching moment CM derived from potentiometer 118 driven by the angle of attack (α) servo-system according to the formula CM (a) p V<SP>2</SP>S/2, a further pitching moment signal MP due to simulated elevator action derived from centre-tapped elevator driven potentiometer 124 energized with antiphased V<SP>2</SP> signals from potentiometer 104 driven by the airspeed (V) servo-system, and a stabilization factor signal (proportional to dh/dt) derived from linear potentiometer 149 of the rate of climb servo-system. Potentiometer 118 is earthed at its centre point, energized with antiphased V2 signals from potentiometer 104, and contoured according to the coefficient of V<SP>2</SP> in the above formula for CM. The servosystem as before operates to reduce the algebraic sum of the input voltages to zero at a displacement representing the rate of pitch (#y) and drives the potentiometer 127 (centre-tapped to earth and energized by antiphased V signals derived from potentiometer 103) to derive a slider voltage FC=V#y representing the gravity component due to centrifugal force which is fed to the input of amplifier 112 as above. Potentiometer 130 is energized by a constant voltage E to derive a slider voltage proportional to rate of pitch #y for the input of the pitch angle (#) servo amplifier 120. Rate of climb simulation.-A similar servosystem computing rate of climb (or dive) dh - comprises an amplifier 145 energizing a dt bi-phase motor 146 and generator 146a geared to drive linear potentiometers 149, 150 ; the amplifier input being energized by a rate feedback signal Efb from the generator, a V sin # signal from slider 143 of potentiometer 142 driven by the pitch angle (#) servo-system, and a V sin α cos # signal derived from the slider of sinusoidal potentiometer 140 driven by the angle of attack (α) servo-system, which is centretapped to earth, and energized by antiphased V cos # signals from sliders 142<SP>1</SP>, 144 of potentiometer 142 driven by the pitch angle (α) servosystem. Potentiometer 149 is earthed at its ends and energized at its centre over a proportioning resistance 155 from the rate signal of the associated generator 146a, so that its slider 147 driven by the servo-system develops a signal proportional to the second derivative of simulated altitude which is fed to the input of the rate of pitch (#y) servo-system 125 to eliminate hunting. Potentiometer 150 is energized by a constant antiphased voltage E, is centre-tapped to earth, and its slider voltage representing the rate of altitude change dh/dt is fed back to the input of servo-amplifier 145, and also energizes an integrating bi-phase motor 152 driving a simulated altimeter 153. The servo-system therefore runs until the algebraic sum of the inputs to amplifier 145 is zeroized at a displacement representing the simulated rate of altitude change dh/dt. The rate of climb servosystem is geared to drive a simulated rate of climb or dive indicator 151. The summation resistances at the inputs of the several servo-system amplifiers have proportions inter se such as to determine the relative amplitudes of the several input quantities, whose respective variations are determined by the slider movements of the potentiometers from which they are derived together with necessary variations of the input voltages thereto. Operation.-In operation the apparatus described is accurately responsive to simulated throttle and elevator settings to compute and display the resultant simulated airspeed, rate of climb, altitude, and aircraft attitude, and also simulates the damped pitching oscillations performed by the simulated aircraft in the vertical plane as a result of variations in such settings, so that in practice the multiple servo-systems are continually operating in directions such as to restore balance in response to the input control quantities, thus simulating the inherent aerodynamic oscillatory equilibrium, and the rate of climb servo-system is continually operative to develop varying voltages representing the second derivative of altitude, which are degeneratively applied as described